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20b20a22f8
When upload-pack serves a client request, it turns to
pack-objects to do the heavy lifting of creating a
packfile. There's no easy way to intercept the call to
pack-objects, but there are a few good reasons to want to do
so:
1. If you're debugging a client or server issue with
fetching, you may want to store a copy of the generated
packfile.
2. If you're gathering data from real-world fetches for
performance analysis or debugging, storing a copy of
the arguments and stdin lets you replay the pack
generation at your leisure.
3. You may want to insert a caching layer around
pack-objects; it is the most CPU- and memory-intensive
part of serving a fetch, and its output is a pure
function[1] of its input, making it an ideal place to
consolidate identical requests.
This patch adds a simple "hook" interface to intercept calls
to pack-objects. The new test demonstrates how it can be
used for debugging (using it for caching is a
straightforward extension; the tricky part is writing the
actual caching layer).
This hook is unlike the normal hook scripts found in the
"hooks/" directory of a repository. Because we promise that
upload-pack is safe to run in an untrusted repository, we
cannot execute arbitrary code or commands found in the
repository (neither in hooks/, nor in the config). So
instead, this hook is triggered from a config variable that
is explicitly ignored in the per-repo config.
The config variable holds the actual shell command to run as
the hook. Another approach would be to simply treat it as a
boolean: "should I respect the upload-pack hooks in this
repo?", and then run the script from "hooks/" as we usually
do. However, that isn't as flexible; there's no way to run a
hook approved by the site administrator (e.g., in
"/etc/gitconfig") on a repository whose contents are not
trusted. The approach taken by this patch is more
fine-grained, if a little less conventional for git hooks
(it does behave similar to other configured commands like
diff.external, etc).
[1] Pack-objects isn't _actually_ a pure function. Its
output depends on the exact packing of the object
database, and if multi-threading is used for delta
compression, can even differ racily. But for the
purposes of caching, that's OK; of the many possible
outputs for a given input, it is sufficient only that we
output one of them.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
62 lines
1.6 KiB
Bash
Executable file
62 lines
1.6 KiB
Bash
Executable file
#!/bin/sh
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test_description='test custom script in place of pack-objects'
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. ./test-lib.sh
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test_expect_success 'create some history to fetch' '
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test_commit one &&
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test_commit two
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'
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test_expect_success 'create debugging hook script' '
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write_script .git/hook <<-\EOF
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echo >&2 "hook running"
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echo "$*" >hook.args
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cat >hook.stdin
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"$@" <hook.stdin >hook.stdout
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cat hook.stdout
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EOF
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'
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clear_hook_results () {
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rm -rf .git/hook.* dst.git
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}
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test_expect_success 'hook runs via global config' '
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clear_hook_results &&
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test_config_global uploadpack.packObjectsHook ./hook &&
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git clone --no-local . dst.git 2>stderr &&
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grep "hook running" stderr
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'
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test_expect_success 'hook outputs are sane' '
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# check that we recorded a usable pack
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git index-pack --stdin <.git/hook.stdout &&
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# check that we recorded args and stdin. We do not check
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# the full argument list or the exact pack contents, as it would make
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# the test brittle. So just sanity check that we could replay
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# the packing procedure.
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grep "^git" .git/hook.args &&
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$(cat .git/hook.args) <.git/hook.stdin >replay
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'
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test_expect_success 'hook runs from -c config' '
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clear_hook_results &&
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git clone --no-local \
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-u "git -c uploadpack.packObjectsHook=./hook upload-pack" \
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. dst.git 2>stderr &&
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grep "hook running" stderr
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'
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test_expect_success 'hook does not run from repo config' '
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clear_hook_results &&
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test_config uploadpack.packObjectsHook "./hook" &&
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git clone --no-local . dst.git 2>stderr &&
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! grep "hook running" stderr &&
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test_path_is_missing .git/hook.args &&
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test_path_is_missing .git/hook.stdin &&
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test_path_is_missing .git/hook.stdout
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'
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test_done
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